In capacitive sensor systems, in particular capacitive proximity sensors, the approach of an object, for example of a finger towards a sensor zone substantially is measured contactless by means of generating and measuring electric alternating fields. Derived from the measurement signal may be functions, for example switching functions, of an electric device, in particular an electric handheld device.
There is a need to provide, for example at an electric handheld device, sensor zones of a capacitive sensor system, wherein during an approach of an object towards a sensor zone not only the approach of the object towards the sensor zone but also the position of the object relative to the sensor zone may be detected.
Depending on the position of the object relative to the sensor zone different functions may be carried out in the electric handheld device. In doing so, a preferably high position resolution is desired. In order that the capacitive sensor system may be applied to different electronic devices, it is further desirable, when the capacitive sensor system preferably is independent of the grounding state of the respective electronic device. Known from prior art are electrode configurations, in particular for capacitive sensor systems, which operate according to the so called loading method, wherein for example for implementing a sliding controller (in a sliding controller it is important that the position of an object, for example a finger, is detectable along the sliding controller) a plurality of sensor electrodes arranged side by side and adjacent, respectively, is provided. During operation of the capacitive sensor using the loading method only one sensor electrode is required, which represents a transmitting electrode as well as also a receiving electrode.
An electric alternating signal is applied to the sensor electrode, so that an electric alternating field is emitted therefrom, wherein the capacitive load of the sensor electrode (for example by an approach of a finger towards the sensor electrode) is detected and evaluated, respectively, by means of an evaluation device. By means of the detected capacitive load it may be determined towards which sensor electrode an approach of the finger has taken place.
Such capacitive sensor systems, however, have the disadvantage that a great many electrodes are required for a high resolution (position resolution), which significantly increases the constructive effort for the production, for example of an capacitive sliding controller. In addition, the sensor signal is dependent on the grounding state of the sensor electronics.
In addition, capacitive sensor systems are known, which also have a great number of sensor electrodes, wherein it is required for an exact detection of the position that for example a finger simultaneously covers several sensor electrodes during contacting the sensor electrodes. Again, the constructive effort for the production here is raised significantly because of the great number of sensor electrodes required for a high position resolution.
Both solutions known from prior art in addition have the disadvantage that the electrodes substantially have to be arranged in one plane, for example at a housing surface of an electric device. However, it is desirable to not arrange the electrodes at the housing, for example to reduce the overhead for the production of the device.